JP3337136B2 - Measuring method in injection molding of metal materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a metal material when a low melting point non-ferrous metal such as zinc, magnesium or an alloy thereof is completely melted and injection-molded in a liquid phase.

[0002]

An attempt has been made to completely melt a non-ferrous metal having a low melting point and to perform injection molding in a liquid phase. As the molding method, as in the case of the plastic material, a heating cylinder equipped with an injection screw rotatable and movable in the axial direction is adopted, and the granular metal material supplied from the rear portion of the heating cylinder is used. It is melted completely by heating while being transferred to the front of the heating cylinder by screw rotation, measured in the liquid phase in the front chamber of the heating cylinder, and then injected into the mold from the nozzle at the tip of the heating cylinder by advancing the screw. Was something.

[0003] Problems to be solved when such injection molding is applied to a metal material are difficulty in material transfer due to screw rotation and instability of measurement. Due to the high viscosity of plastic materials due to melting, transfer by screw rotation is mainly due to the fact that the friction coefficient at the interface between the molten plastic and the screw is smaller than the friction coefficient at the interface between the molten plastic and the inner wall of the heating cylinder, and there is friction It arises from the fact that there is a coefficient difference.

On the other hand, a metal material completely melted to a liquid phase has a viscosity that is incomparably lower than that of plastic, so that there is almost no difference in friction coefficient between the two interfaces. Transfer force due to screw rotation unlike plastic is unlikely to occur.

[0005] Even in the case of a metallic material, a transfer force is generated in a high viscosity region in a semi-molten state in the process of solid transfer and melting, so that transfer to the region can be performed by screw rotation. Therefore, the viscosity decreases and the transfer force due to the screw groove between the screw flights decreases, so that it becomes difficult to stably supply the heating cylinder to the front chamber by the screw rotation.

[0006] In addition, since the plastic material becomes high in viscosity due to melting, the material pressure is stored in the front chamber of the heating cylinder by the rotation of the screw, and as a reaction force, a material pressure for pushing the screw backward is generated. By controlling the screw retreat due to, the amount of the molten material can be made constant every time.

However, when the metal material has a low viscosity in a liquid phase, the pressure does not increase enough to push the screw backward, so that the screw is unlikely to be retracted due to the material pressure, and the amount of storage in the front chamber can be reduced only by rotating the screw. Differently, it cannot be constant every time.

[0008] In addition, since the specific gravity of a metal material is significantly higher than that of a plastic material, and it has a low viscosity and fluidity in a liquid state, when the screw rotation is stopped and stopped in a horizontally installed heating cylinder, the liquid phase The metal material in the state leaks from the clearance between the screw flight and the heating cylinder to the rear half-melted region, and accordingly, the metal material accumulated in the front chamber also moves from the ring valve in the open state to the front of the screw. The amount of water is reduced by flowing back around the part.

As the accumulated amount decreases, the liquid phase level also decreases in the front chamber, so that a gas phase (gap) that makes measurement unstable is generated in the upper part of the front chamber, and the leaked liquid phase material is in a semi-molten region. The temperature decreases to increase the viscosity, or depending on the heating state of the semi-molten region, solidifies to form a weir in the screw groove, which hinders the transfer of the granular material from the supply port behind by screw rotation. There is also the problem of coming.

The present invention has been conceived in order to solve the above-mentioned problem in the case of injection molding a metal material in a liquid phase state, and has as its object the inclination installation of a heating cylinder and the forced retreat of a screw. Accordingly, it is an object of the present invention to provide a new method of measuring a metal material in injection molding, which can always smoothly transfer, measure, and deaerate a metal material in a liquid phase.

[0011]

SUMMARY OF THE INVENTION According to the present invention, there is provided a heating cylinder having a nozzle at a tip end and a supply port at a rear end, wherein a screw is rotatably and axially movable, and a metal in the heating cylinder is provided. After the material is transferred to the front chamber of the heating cylinder in the liquid phase by melting and weighed, in the injection molding of the metal material injected from the nozzle by the screw advancement, the heating cylinder is moved forward by its own weight in the liquid phase in the liquid state. The liquid phase material is installed inclined downward so that it flows down into the chamber, and while maintaining the inclined state, the screw at the advanced position after injection is forcibly retracted to the set position and the liquid phase material temporarily stored around the front of the screw Quantitation,
After suctioning and accumulating in the front chamber of the heating cylinder by negative pressure, the screw at the retreat position is stopped and then rotated to measure the liquid phase material in the front chamber to a constant amount each time.

The screw has a plunger for injection at a tip thereof, and the plunger has substantially the same diameter as a reduced diameter front chamber formed in the front end portion of the heating cylinder. Is formed so that it can be inserted into the front chamber so as to be able to move forward and backward, and a sensor for measuring the number of rotations of the screw is provided. Is controlled to the set number of times.

[0013]

FIG. 1 shows an example of an injection molding machine used for carrying out the present invention. In the figure, reference numeral 1 denotes an injection device of an in-line screw type, and 2 denotes a mold clamping device of a normal configuration opposed to the injection device 1, and a fixing plate 21 of the mold clamping device 2.
The movable plate 22 and the movable plate 22 are provided with a pair of split molds 4.

The injection device 1 is, as schematically shown in FIG.
An injection screw 12 is rotatably and axially movable in a heating cylinder 11 having band heaters (not shown) mounted at regular intervals on the outer periphery. The heating cylinder 11 has a nozzle 13 at the tip and a supply port 14 for granular metal material at the rear.
The nozzle 13 is tilted downward so that the molten metal in the liquid phase in the heating cylinder flows down into the front chamber by its own weight with the supply port 14 on the upper side.

The screw 12 is a normal screw in which a ring valve 15 for backflow prevention is fitted to the outer periphery of a conical tip so as to be able to advance and retreat, and has no compression portion. With a screw groove of a predetermined pitch between the swirled flights, the metal material from the supply port 14 is transferred to the front of the heating cylinder by screw rotation.

Such an injection device 1 and the mold clamping device 2
Is that the metal material in the liquid phase in the heating cylinder 11 flows down to the front chamber 11a of the heating cylinder 11 by its own weight, and the nozzle 13 is bent when the sprue bush 41 in the mold 4 is positioned on the same straight line. In order to perform the nozzle touch without performing, the mold 4 is inclinedly installed at the same angle (at least an inclination angle of 3 degrees or more) on the machine base 3 with the mold 4 side lower.

Since the present invention can be practiced even when only the injection device 1 is installed at an angle, the injection device 1 and the mold clamping device 2 are preferably installed at the same angle as in the embodiment. It is not limited.

FIG. 2A schematically shows the melting state of the metal material at the screw advance position after injection.
From the rear, there are the granular material a, semi-molten material b, and liquid phase material c. From these states, the metal material is first screw-transferred and transferred as a granular material a to the front of the heating cylinder by the screw rotation at the time of measurement, and is melted by heating from the outside in the middle thereof to form a solid phase and a liquid phase. The mixed semi-solid material b is obtained.

In the semi-molten material b, when the liquid phase ratio is increased by further heating, the liquid-phase material c having a low viscosity like hot water
Only the heating of the heating cylinder 11 with the screw 12 is downwardly inclined together with the screw 12, so that the liquid material c is transferred to the front of the screw 12 because the heating cylinder 11 is inclined downward together with the screw 12. It is stored so as to flow down to the surroundings to increase the depth, and deaeration is naturally performed.

A gaseous phase d is generated between the material b and the semi-molten material b. Since the semi-molten material b is located above the liquid phase surface which faces horizontally to the gaseous phase d, the screw rotates. Even when stopped and stopped, the liquid phase material c does not leak to the semi-molten material b side, and therefore, the accumulated amount of the front chamber 11a does not fluctuate.

FIG. 2B shows a state in which the liquid material c stored around the front of the screw 12 is transferred to the front chamber 11 of the heating cylinder 11.
This shows a state in which weighing is performed by forcibly supplying the weighing unit to a.
This measurement is performed by forcibly retracting the screw 13 at a set distance backward without rotating the screw 12 at the advanced position after injection in a state where the nozzle 13 is in nozzle contact with the sprue bush 41 of the mold 4.

By the forced retreat, the front chamber 1 of the heating cylinder 11 is
1a is a negative pressure state (decompression or vacuum state) because the nozzle tip is blocked by the material solidified by cooling after the previous injection, and the closed ring valve 15 is pulled back to open. At the same time, the liquid phase material c temporarily stored around the front part of the screw 12 is sucked into the front chamber 11a by suction.
It flows into and accumulates. This suction does not reach the semi-molten material b due to the gas phase d between the semi-molten material b and the liquid phase material c, and the vapor phase d is enlarged.

In the accumulation by suction, depending on the amount of the temporarily stored liquid-phase material c, air or the like may reach the gaseous phase d, and may be temporarily stored around the front part of the screw 12. Since the amount of the liquid-phase material c also decreases and the next measurement may be insufficient, replenishment and deaeration of the liquid-phase material c by screw rotation are performed.

FIG. 2C shows the replenishment state. When the screw 12 has retreated to a preset position, the screw 12 is stopped and rotated at that position. Due to this rotation, the granular material a at the rear of the screw is transferred to the front to be in a semi-molten state, and the semi-molten material b at the front is further heated and melted into a liquid phase while being transferred, and stored around the front of the screw 12. In addition to increasing the amount of the liquid phase material c, if there is a shortage in the liquid phase material c accumulated in the anterior chamber 11a, the shortage is compensated and the measurement is stabilized every time, and Degassing due to its own weight is also performed.

The primary storage amount of the liquid material c differs depending on the screw rotation speed (rpm) and the rotation time (s). Therefore, it is preferable to measure the screw rotation speed (rpm) with a sensor and control the number of rotations to a set number. Specifically, a certain number of rotations from the start of screw rotation is counted and measured by a tachometer (sensor) used in a normal molding machine, and is calculated from the screw rotation number (rpm) × rotation time (s). The number of rotations is calculated and controlled to the set number of times. The rotation of the screw is preferably performed with a certain back pressure to prevent the screw from retreating during rotation.

When the replenishment by the screw rotation is completed, the screw rotation is stopped, the process is switched to the injection, and the screw 12 is moved forward by the process control, and the front chamber 1 is moved.
The liquid material c measured in 1 a is injected into the mold 4. The solidified material that has closed the nozzle tip at the time of this injection is extruded toward the mold by the injection pressure, so that it does not hinder the injection filling of the liquid phase material c accumulated in the front chamber 11a. The screw 12 moves to the injection completion position shown in FIG. Then, the process is switched again to the next measurement, and the screw 12 is forcibly retracted.

In molding a product having a small injection amount, a large number of primary storage amounts of the liquid phase material c can be set so that a plurality of shots can be continuously performed. Only one shot for multiple shots.

FIG. 3 shows an embodiment in which the tip is formed as an injection plunger and the injection device is provided with a screw 12 in which the ring valve 15 is omitted. The heating cylinder 11 of this injection device is reduced in diameter by about 8 to 15% with respect to the inner diameter of the heating cylinder over a required length in the distal end portion.
It is formed in the front chamber 11a for measurement. The tip has a nozzle 13 similarly to the above embodiment.

The screw 12, which is rotatably and axially movable inside the heating cylinder 11, has a plunger 16 for injection at the tip. The diameter of the plunger 16 is substantially the same as the diameter of the front chamber 11a, so that the plunger 16 slides to such an extent that the backflow of the liquid phase material c in the front chamber 11a shown in FIG. 3 hardly occurs. It is inserted into the front room 11a so as to be able to move forward and backward while securing the dynamic clearance.

The distal end portion 17 of the plunger 16 is formed in a conical shape with a tapered surface adapted to the funnel-shaped distal end portion of the front chamber 11a, and a plurality of flow grooves 18 extend between the tapered surface and the front portion of the shaft. It is recessed at regular intervals. In addition,
The flow groove 18 is not always necessary, and the retreat position of the screw 2 is behind the position shown in FIG.
Can be omitted if a flow gap is formed around the periphery.

The screw 12 is connected to the plunger 16
The front chamber 11a is moved forward by the process control until the leading end 17 reaches the filling completion position, and the liquid material c measured therein is injected and filled into the mold 7 except for a required amount as a cushion. I do. The material measurement after the injection is performed by forcibly retracting the screw 13 at the set position after the injection without rotating the screw 12 at the advanced position after the injection in a state where the nozzle 13 is in nozzle contact with the sprue bush 41 of the mold 4. Done.

By the forced retreat, the front chamber 1 of the heating cylinder 11
1a is a liquid temporarily stored around the front of the screw 12 in a negative pressure state (decompression or vacuum state) because the nozzle tip is closed by the material solidified by cooling after the previous injection. The phase material c flows into the front chamber 11a by suction and accumulates. Subsequent steps are the same as those of the embodiment described with reference to FIG. 2, and thus the detailed description thereof is omitted.

As described above, in the weighing method of the present invention,
With the suction force due to the negative pressure generated by the forced retreat of the screw, the metallic material in the liquid phase temporarily stored around the front of the screw accumulates in the front chamber of the heating cylinder. Transfer to the anterior chamber can be performed simply and reliably.

Further, since the heating cylinder is inclined downward to accumulate the metal material in the front chamber, even if the metal material is in a low-viscosity liquid phase, there is no fluctuation in the accumulation amount due to the backflow. The subsequent rotation of the screw allows temporary storage in the liquid phase and replenishment of the accumulated amount in the anterior chamber. However, it is possible to obtain a product using a stable metal material.

[Brief description of the drawings]

FIG. 1 is an elevational view of a metal material injection molding machine used for carrying out a measuring method of the present invention.

FIG. 2 is a schematic explanatory view of a main part of an injection device showing a measuring method of the present invention in the order of steps.

FIG. 3 is a longitudinal sectional view of a tip end of an injection device provided with a screw of another embodiment in which a ring valve is omitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection apparatus 2 Mold clamping mechanism 3 Machine base 4 Die 11 Heating cylinder 11a Front chamber of heating cylinder 12 Screw 13 Nozzle 14 Supply port 15 Ring valve 16 Plunger 17 Tip part a Granular material b Semi-molten material c Liquid phase material d gas phase

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahiro Kobayashi 2110, Nanjo, Nanjo, Hanashi-gun, Nagano Prefecture Nissei Plastic Industry Co., Ltd. Inside (72) Inventor Mamoru Miyagawa 2110 Nanjo, Oaza, Hanagi-gun, Hanishina-gun, Nagano Nissei Plastic Industry Co., Ltd. (56) References JP-A-9-108805 (JP, A) JP-A-11-47901 (JP) , A) JP-A-7-156227 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 17/32 B22D 17/20 B22D 17/30

Claims (3)

(57) [Claims] A screw is rotatably and axially movable in a heating cylinder having a nozzle at a tip and a supply port at a rear part, and a metal material in the heating cylinder is melted in a liquid phase by melting. In the injection molding of the metal material injected from the nozzle by the screw advance after transferring to the front chamber and weighing, the heating cylinder is inclined downwardly installed so that the metal material flows down to the front chamber by its own weight in a liquid state. The screw in the forward position after the injection is forcibly retracted to the set position while maintaining the inclined state, and a predetermined amount of the liquid phase material temporarily stored around the front of the screw is reduced by the negative pressure to the front chamber of the heating cylinder. A method for measuring the amount of liquid phase material in a front chamber by metering a fixed amount of liquid material in a front chamber each time after stopping a screw at a retreat position after accumulating and accumulating the liquid material. 2. The injection molding method of a metal material according to claim 1, wherein a sensor for measuring the number of revolutions of the screw is provided, and the number of revolutions is controlled to a set number of times by the sensor. Weighing method. 3. The screw has a plunger for injection at a tip thereof, the plunger having substantially the same diameter as a front chamber formed by reducing the diameter in a front end portion of the heating cylinder, and having a liquid phase material in the front chamber. 2. The method according to claim 1, wherein the sliding clearance is such that backflow hardly occurs, and is formed so that it can be inserted into the front chamber so as to be able to advance and retreat.